Page 585 - Polymer-based Nanocomposites for Energy and Environmental Applications

538 Polymer-based Nanocomposites for Energy and Environmental Applications

of 2 mS/cm [137]. Other strategies have also been developed to improve the char-
acteristics of polymer electrolytes by replacing PEO with PEO copolymers or
PEO derivatives on an inorganic core [138]. Among the composites with an inorganic
core, the use of a POSS could efficiently enhance the mechanical strength and
the chemical stability of the composites, but the ionic conductivity remains low
( 0.1 mS/cm) [139].
– Gel polymer electrolytes
In the electrolytes, a small quantity of polymer is incorporated to carbonate solvents to
form a gel, which behaves like a nonaqueous liquid electrolyte. Because of this par-
ticular state, ion movement is easier than in a solid electrolyte, and the ionic conduc-
tivity is high (>1 ms/cm). PVDF and polyacrylonitrile (PAN) are commonly used in
gel polymer electrolytes. For instance, PVDF with LiPF 6 and LiCF 3 SO 3 provides a
high-ionic conductivity reaching 50 mS/cm [140]. Thermal and mechanical properties
of the polymer membrane could be improved by blending PVDF with
hexafluopropene yielding a higher ionic conductivity than that of PVDF. As well,
PAN can be electrodeposited on nanotubular TiO 2 to improve the stability of the elec-
trode in LIBs [141] by creating an efficient conducting path for the ionic transport at
the electrolyte/electrode interface.
LIB technology has been developed for renewable energy storage with a rapid
expansion and becomes dominant on the electronic market and on the automotive
transportation industry. Several parameters of the devices need to be optimized for
assuring a high-specific energy, a high power, and a high safety and reliability. Solu-
tions have been successfully proposed to optimize the mechanical and electrochem-
ical quality of electrodes and electrolytes, which are the essential elements of LIBs:
(i) use of nanostructured electrodes with modified morphologies, (ii) use of polymer-
based composites including gel polymer for electrolytes, and (iii) design of fully flex-
ible batteries. Nevertheless, important issues should be addressed in the near future to
make LIBs definitively universal tools for energy storage. These issues relate on the
one hand to the commercial exploitation of Li that remains expensive and would be
compensated by a higher performance of batteries. Safety of devices in operation on
the other hand is still a challenge for successful use in practical applications. Some
recent advanced technologies on Li-air or Li’sulfur, whose energy density would
be higher than 3700 Wh/kg [142], may provide promising solutions to a bright future
of these devices.

19.3.2.3 Hybrid nanocomposites for energy savings
As we have seen in the first part of this section, nanocomposite materials can be used
for producing energy from natural sources without negative impact on the environ-
ment. Furthermore, they can provide efficient pathways to preserve the excess of pro-
duced energy in order to reuse it whenever needed. Both actions benefit the
environment while providing comforts to human and companies for everyday energy
need. From the energy point view, another approach for preserving nature consists of
controlling the energy consumption, in particular the electricity generation, which